Various errors occur in the data transmission of communication system by the influence of random noise or multipath fading in wireless transmission, etc. the channel coding could provide a reliable communication in the communication channel with noise. Currently, the low density parity check code (LDPC) has been considered as one of the best error correction coding methods for the excellent performance and efficient decoding algorithm.
LDPC code is a linear error correction code on the basis of sparse parity check matrix H, the elements in H is either 0 or 1. if N represents the length of LDPC code, K represents the length of information bits, M represents the length of check bits, γ represents the row weight, λ represents the column weight, R represents the code rate, that LDPC code could be expressed as (N,K) LDPC code. If γ and λ are constants, the LDPC code is regular LDPC code, otherwise, it is irregular LDPC code.
The codeword of LDPC code is the zero space of the check matrix H thereof, the encoding process is described as follows: first, constructing parity check matrix H by the parity check matrix constructing unit, on the basis of the preset LDPC encoding parameter; then, obtaining generating matrix G by the generating matrix constructing unit, on the basis of check matrix H, wherein, generating matrix G and the corresponding check matrix H are dual matrix; finally, encoding the input data s by generating matrix G and obtaining the output LDPC codeword c by the encoding unit.
From the practical point, one important reason of restricting the wide use of LDPC code is: the sparse parity check matrix and the non-sparse parity check matrix take too much storage space, which causes that the encoding of LDPC code need too much storage space. Besides, the exorbitant complexity of the traditional encoding process is another reason to limit the wide use of LDPC code. The LDPC code has not been widely used for the existence of the above drawbacks.